Apparatus for electrochemically generating oxygen

ABSTRACT

The present invention relates to an oxygen generating apparatus comprising: a membrane-electrode assembly including an anode connected to a first pole of a power supply device, a cathode connected to a second pole of the power supply device, and an electrolyte membrane provided between the anode and the cathode; a water supply source for supplying water to the anode; and an oxygen supply unit for supplying oxygen to the cathode, wherein oxygen (O 2 ) is generated at the anode by using an oxygen evolution reaction (OER) and water (H 2 O) is generated at the cathode by using an oxygen reduction reaction (ORR). The present invention may provide an apparatus for electrochemically generating oxygen, which uses an electrochemical method and thus can generate oxygen without noise or vibration, and has a simple configuration capable of reducing the volume of the apparatus.

CROSS-REFERENCE TO RELATED APPLICATION

This application is the National Stage of International Application No.PCT/KR2018/008438, filed on Jul. 25, 2018, which claims the benefit ofand priority to Korean Patent Application No. 10-2017-0094511 filed onJul. 26, 2017 and Korean Patent Application No. 10-2018-0076331 filed onJul. 2, 2018, which are herein incorporated by reference in theirentirety.

TECHNICAL FIELD

The present invention relates to an electrochemical oxygen generator,and more particularly, to an electrochemical oxygen generator applicableto various fields such as in portable, domestic, medical, vehicular, orindustrial oxygen generating devices, oxygen pumps, oxygen compressors,or oxygen concentrators.

TECHNICAL BACKGROUND

Recently, as atmospheric contamination has intensified due toenvironmental problems or the like, oxygen-related products are beingattracted attention.

In general, oxygen is an essential element for the survival ofhumankind, and in various fields, technology for generating high purityoxygen as needed is being considered to be very important.

For example, oxygen generators are applied to various fields such as inportable, domestic, medical, vehicular, or industrial oxygen generatingdevices, oxygen pumps, oxygen compressors, or oxygen concentrators.

Such an oxygen generator uses the conventional pressure swing adsorption(PSA) method, membrane separation method, or oxygen generatingtechnology using an oxygen tank.

However, the conventional oxygen generating technology such as the PSAmethod or the membrane separation method is highly expensive due to alarge size of a system due to a complicated oxygen generating processand use of a large amount of an adsorbent or the like. In addition, inthe case of these methods, since a compressor should be used, noise andvibration inevitably occur.

Accordingly, in the case of the oxygen generator using the PSA method orthe membrane separation method, it is difficult to miniaturize theoxygen generator and it is difficult to popularize the oxygen generatorbecause the oxygen generator cannot be used in a space requiring quietoperation.

In addition, the oxygen generator using the oxygen tank has advantagesin that it is possible to lower the price of the oxygen generator,miniaturize the oxygen generator, and implement noise-free andvibration-free oxygen generation but has a problem in that the oxygentank should be periodically filled with oxygen from a specialized gascompany in accordance with the use of the oxygen generator. Furthermore,the oxygen generator has a problem in that it is very inconvenient touse the oxygen generator due to the usage time of the oxygen generatorbeing limited to the size of the oxygen tank.

DETAILED DESCRIPTION Problems to be Solved

The present invention is directed to providing an electrochemical oxygengenerator capable of generating oxygen without noise and vibration usingan electrochemical method and being manufactured as a miniaturizeddevice.

Objects of the present invention are not limited to the objectsdescribed above, and other objects that are not described will beclearly understood by a person skilled in the art from the descriptionbelow.

Solution to Solve the Problem

One aspect of the present invention provides an oxygen generator,wherein an oxygen reduction reaction occurs at a cathode to whichoutside air is introduced, an oxygen evolution reaction occurs at ananode to which water is supplied, and an air flow rate at which theoutside air flows is 20 ccm or more.

Oxygen (O₂) may be generated at the anode using the oxygen evolutionreaction (OER), and water (H₂O) may be generated at the cathode usingthe oxygen reduction reaction (ORR).

Another aspect of the present invention provides an oxygen generatorincludes a membrane-electrode assembly including an anode connected to afirst electrode of a power supply, a cathode connected to a secondelectrode of the power supply, and an electrolyte membrane providedbetween the anode and the cathode, a water supply source configured tosupply water to the anode, and an air supply unit configured to supplyoxygen to the cathode, wherein oxygen (O₂) is generated at the anodeusing an OER, and water (H₂O) is generated at the cathode using an ORR.

The oxygen generator may further include a water collection lineconfigured to collect water (H₂O) generated at the cathode in the watersupply source.

The oxygen generator may further include a first outer frame portionpositioned outside the anode and a second outer frame portion positionedoutside the cathode, wherein the first outer frame portion includes afirst outer frame, a water inlet positioned at one side of the firstouter frame, and an oxygen outlet positioned at the other side of thefirst outer frame, and the second outer frame portion includes a secondouter frame, an oxygen inlet positioned at one side of the second outerframe, and a water outlet positioned at the other side of the secondouter frame.

Water (H₂O) supplied from the water supply source may be supplied to theanode through the water inlet, hydrogen ions (H⁺), oxygen (O₂), andelectrons may be generated by electrolyzing water (H₂O) and thegenerated oxygen (O₂) may be discharged through the oxygen outlet at theanode, and oxygen (O₂) in air supplied from the oxygen inlet may reactwith hydrogen ions (H⁺) being moved by passing through the electrolytemembrane to generate water (H₂O) and the generated water (H₂O) may bedischarged through the water outlet at the cathode.

The anode may include a first support and a first catalyst layerpositioned at one side of the first support, the first support mayinclude carbon black, Ketjen black, acetylene black, an activated carbonpowder, a carbon molecular sieve, carbon nanotubes, activated carbonhaving fine pores, mesoporous carbon, a conductive polymer, or a mixturethereof, and the first catalyst layer may include at least one catalystfor an OER selected from the group consisting of metals includingplatinum (Pt), iridium (Ir), ruthenium (Ru), nickel (Ni), manganese(Mn), cobalt (Co), iron (Fe), titanium (Ti), rhenium (Re), niobium (Nb),vanadium (V), sulfur (S), and molybdenum (Mo) and the metals combinedwith an oxide, a nitride, a carbide, a phosphide, and a sulfide.

The cathode may include a second support and a second catalyst layerpositioned at one side of the second support, the second support mayinclude at least one material selected from the group consisting ofcarbon or transition metals combined with an oxide, a nitride, acarbide, a phosphide, and a sulfide, and the second catalyst layer mayinclude at least one catalyst for an ORR selected from the groupconsisting of platinum (Pt), palladium (Pd), iridium (Ir), gold (Au),silver (Ag), and alloys thereof.

The cathode may include a second support and a second catalyst layerpositioned at one side of the second support, the second support mayinclude at least one material selected from the group consisting ofcarbon or transition metals combined with an oxide, a nitride, acarbide, a phosphide, and a sulfide, and the second catalyst layer mayinclude an Fe—N—C catalyst.

The Fe—N—C catalyst may inhibit a hydrogen evolution reaction andpromote an ORR.

Advantages of Invention

In the present invention, it is possible to constitute an oxygengenerator for generating oxygen (O₂) using a simple configurationincluding a membrane-electrode assembly, a power supply capable ofapplying a certain amount of power, and a water supply source capable ofsupplying water to an anode of the membrane-electrode assembly.

Therefore, in the present invention, an electrochemical oxygen generatorcan be provided such that oxygen is generated without noise andvibration using an electrochemical method and the electrochemical oxygengenerator is also miniaturized due to a simple device configuration.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram for describing a principle of an oxygengenerator according to the present invention.

FIG. 2 is a schematic exploded perspective view illustrating anapplication example of an oxygen generator according to the presentinvention.

FIG. 3 is a partially assembled perspective view illustrating theapplication example of the oxygen generator according to the presentinvention.

FIG. 4 is a schematic view illustrating an assembled state of theapplication example of the oxygen generator according to the presentinvention excluding a gasket.

FIG. 5 is a graph showing a change in oxygen generation current densityaccording to a voltage of Experimental Example 1.

FIG. 6 is a graph showing a change in oxygen generation current densityaccording to a voltage of Experimental Example 2.

FIG. 7 is a graph showing a change in oxygen generation current densityaccording to a voltage of Experimental Example 3.

FIG. 8 is a graph showing a change in oxygen generation current densityaccording to a voltage of Experimental Example 4.

FIG. 9 is a graph showing a change in oxygen generation current densityaccording to a flow rate of air of Experimental Example 5.

FIG. 10 is a graph showing a change in oxygen generation current densityaccording to a voltage of Experimental Example 6.

FIG. 11 is a graph showing a change in oxygen generation current densityaccording to a voltage of Experimental Example 7.

FIG. 12 is a graph showing a change in oxygen generation current densityaccording to a voltage of Experimental Example 8.

EMBODIMENTS

Advantages and features of the present invention and methods foraccomplishing the same will be more clearly understood from embodimentsdescribed in detail below with reference to the accompanying drawings.However, the present invention is not limited to the followingembodiments but may be implemented in various different forms. Theembodiments are provided only to complete the present invention and tofully provide a person having ordinary skill in the art to which thepresent invention pertains with the category of the present invention,and the present invention will be defined by the appended claims.

Hereinafter, specific contents for carrying out the present inventionwill be described in detail with reference to the accompanying drawings.The same reference numeral indicates the same element regardless of thedrawings. With respect to the elements referred using the term of“and/or”, each of the elements and all possible combinations of theelements are included in the present invention.

It should be understood that, although terms such as “first,” “second,”and the like may be used herein to describe various components, thesecomponents are not limited by these terms. These terms are only used todistinguish one element or component from another element or component.Therefore, a first component described below could be termed a secondcomponent without departing from the scope and spirit of the presentinvention.

The terms used in the present specification are for explaining theembodiments rather than limiting the present invention. As used herein,singular expressions, unless defined otherwise in contexts, includeplural expressions. The meaning of “comprises” and/or “comprising” usedin this specification does not exclude the existence or addition of oneor more other components in addition to the mentioned components.

Unless otherwise defined, all terms (including technical and scientificterms) used in the present specification may be used as the same meaningwhich may be commonly understood by the person with ordinary skill inthe art to which the present invention belongs. It will be furtherunderstood that terms defined in commonly used dictionaries should notbe interpreted in an idealized or excessive sense unless expressly andspecifically defined.

Spatially relative terms, such as “below,” “beneath,” “lower,” “above,”“upper” and the like, may be used to easily describe relationshipsbetween one component and another component as shown in the drawings. Itwill be understood that the spatially relative terms are intended toencompass different orientations of components in use or in operation,in addition to the orientation depicted in the drawings. For example, ifa component shown in the drawing is turned over, a component describedas “below,” “beneath,” or “under” another component would then beoriented “above” another component. Thus, the exemplary term “below” canencompass both an orientation of above and below. Since a component maybe oriented in another direction, the spatially relative terms may beinterpreted in accordance with the orientation of the component.

Hereinafter, exemplary embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

Prior to describing an electrochemical oxygen generator according to thepresent invention, a general water electrolysis reaction and fuel cellreaction will be described.

Water Electrolysis Reaction

Anode: 2H₂O→O₂+4H⁺+4e ⁻  (OER)

Cathode: 4H⁺⁺4e ⁻→2H₂  (HER)

Fuel Cell Reaction

Anode: O₂+4H⁺+4e ⁻→2H₂O  (ORR)

Cathode: 2H₂→4H⁺+4e ⁻  (HOR)

That is, in the case of the general water electrolysis reaction, anoxygen evolution reaction (OER) occurs at an anode, and a hydrogenevolution reaction (HER) occurs at a cathode.

In addition, in the case of the general fuel cell reaction, an oxygenreduction reaction (ORR) occurs at an anode, and a hydrogen oxidationreaction (HOR) occurs at a cathode.

However, in the oxygen generator according to the present invention, thefollowing reactions occur in an anode and a cathode.

Oxygen Generator of the Present Invention

Anode: 2H₂O→O₂+4H⁺+4e ⁻  (OER)

Cathode: O₂+4H⁺+4e ⁻→2H₂O  (ORR)

That is, in the present invention, oxygen (O₂) is generated at the anodeusing an OER that is a water electrolysis reaction, and water (H₂O) isgenerated at the cathode using an ORR that is a fuel cell reaction.

FIG. 1 is a schematic diagram for describing a principle of an oxygengenerator according to the present invention.

Referring to FIG. 1, an oxygen generator 10 according to the presentinvention includes a membrane-electrode assembly 60 including an anode30 connected to a first electrode of a power supply 20, a cathode 40connected to a second electrode of the power supply, and an electrolytemembrane 50 provided between the anode and the cathode. In this case,the first electrode may be a positive electrode, and the secondelectrode may be a negative electrode.

In addition, the oxygen generator 10 according to the present inventionincludes a water supply source 70 for supplying water to the anode 30and an air supply unit 80 for supplying oxygen to the cathode 40.

In this case, the air supply unit 80 may be for supplying oxygen to thecathode 40 and may supply general air to the cathode to supply oxygen tothe cathode 40.

Meanwhile, the supply of oxygen by the air supply unit 80 may beunderstood to mean that air is supplied to the cathode 40. In order tosupply oxygen to the cathode 40 by supplying air to the cathode 40, theair supply unit 80 may use a known fan, but a type of the air supplyunit 80 is not limited thereto.

That is, air may be forcibly supplied to the cathode 40 by operating thefan, thereby supplying oxygen to the cathode 40.

In the present invention, the supply of oxygen through such a forciblemethod may be expressed as an air flow rate, which will be describedbelow.

On the other hand, as described above, the following reactions occur atthe anode and the cathode of the membrane-electrode assembly 60according to the present invention.

Anode: 2H₂O→O₂+4H⁺+4e ⁻  (OER)

Cathode: O₂+4H⁺+4e ⁻→2H₂O  (ORR)

That is, in the present invention, at the anode, hydrogen ions (H⁺),oxygen (O₂), and electrons are generated by electrolyzing water (H₂O)supplied from the water supply source 70.

In this case, hydrogen ions (H⁺) generated at the anode move to thecathode by passing through the electrolyte membrane 50.

At the cathode, oxygen (O₂) in air supplied from the air supply unit 80reacts with hydrogen ions (H⁺) being moved by passing through theelectrolyte membrane 50 to generate water (H₂O).

That is, in the present invention, at the anode, oxygen (O₂) isgenerated using an OER, and at the cathode, water (H₂O) is generatedusing an ORR.

Meanwhile, the oxygen generator 10 according to the present inventionmay further include a water collection line 90 for collecting water(H₂O) generated at the cathode 40 in the water supply source 70. On theother hand, in the drawing, water (H₂O) generated at the cathode 40 isillustrated as being collected in the water supply source 70, but water(H₂O) generated at the cathode 40 may be discharged through anydischarge line.

However, in the present invention, since it is necessary to supply water(H₂O) to the anode from the water supply source 70, that is, the watersupply source 70 corresponds to an essential component, water (H₂O)generated at the cathode 40 may be collected in the water supply source70.

In the present invention, through the reactions at the anode and thecathode as described above, it is possible to constitute the oxygengenerator for generating oxygen (O₂) at the anode.

That is, oxygen (O₂) generated at the anode may be applied to variousfields such as in portable, domestic, medical, vehicular, or industrialoxygen generating devices, oxygen pumps, oxygen compressors, or oxygenconcentrators.

In this case, as can be seen in the above-described oxygen generatoraccording to the present invention, it is possible to constitute theoxygen generator for generating oxygen using a simple configurationincluding the membrane-electrode assembly 60 including the anode 30, thecathode 40, and the electrolyte membrane 50 provided between the anodeand the cathode, the power supply 20 capable of applying a certainamount of power to the anode and the cathode, the water supply source 70capable of supplying water to the anode, and the air supply unit 80 forsupplying oxygen to the cathode 40.

As described above, among oxygen generating technologies forimplementing the conventional oxygen generators, a pressure swingadsorption (PSA) method, a membrane separation method, or the like ishighly expensive due to a large size of a system due to a complicatedoxygen generating process and use of a large amount of an adsorbent orthe like. In addition, in the case of these methods, since a compressorshould be used, noise and vibration inevitably occur.

In addition, an oxygen generator using an oxygen tank has a problem inthat the oxygen tank should be periodically filled with oxygen from aspecialized gas company in accordance with the use of the oxygengenerator.

However, in the present invention, it is possible to constitute theoxygen generator for generating oxygen (O₂) using a simple configurationincluding the membrane-electrode assembly 60, the power supply 20capable of applying a certain amount of power, the water supply source70 capable of supplying water to the anode of the membrane-electrodeassembly, and the air supply unit 80 for supplying oxygen to the cathodeof the membrane-electrode assembly.

Therefore, in the present invention, an electrochemical oxygen generatorcan be provided such that oxygen is generated without noise andvibration using an electrochemical method and the electrochemical oxygengenerator is also miniaturized due to a simple device configuration.

Hereinafter, an application example of the oxygen generator according tothe present invention will be described.

FIG. 2 is a schematic exploded perspective view illustrating anapplication example of an oxygen generator according to the presentinvention. FIG. 3 is a partially assembled perspective view illustratingthe application example of the oxygen generator according to the presentinvention. FIG. 4 is a schematic view illustrating an assembled state ofthe application example of the oxygen generator according to the presentinvention except for a gasket.

However, the application example of the oxygen generator according tothe present invention that will be described below is merely illustratedas an example to which the above-described principle of the oxygengenerator according to the present invention of FIG. 1 is applied, andthus, the scope of the present invention is not limited to theapplication example of the oxygen generator of FIGS. 2 and 3.

In addition, in the application example of the oxygen generatoraccording to the present invention of FIGS. 2 to 4, the same componentsas those described above with reference to FIG. 1 are denoted by thesame reference numerals.

Referring to FIGS. 2 to 4, an application example 100 of an oxygengenerator according to the present invention includes amembrane-electrode assembly 60 including an anode 30 connected to afirst electrode of a power supply 20, a cathode 40 connected to a secondelectrode of the power supply, and an electrolyte membrane 50 providedbetween the anode and the cathode. In this case, the first electrode maybe a positive electrode, and the second electrode may be a negativeelectrode.

In addition, the application example 100 of the oxygen generatoraccording to the present invention includes a water supply source 70 forsupplying water to the anode 30 and an air supply unit 70 for supplyingoxygen to the cathode 40.

In this case, as described above, the air supply unit 70 may be forsupplying oxygen to the cathode 40, and the air supply unit 80 maysupply general air to the cathode to supply oxygen to the cathode 40.

Meanwhile, the supply of oxygen by the air supply unit 80 may beunderstood to mean that air is supplied to the cathode 40. In order tosupply oxygen to the cathode 40 by supplying air to the cathode 40, theair supply unit 80 may use a known fan, but a type of the air supplyunit 80 is not limited thereto.

That is, air may be forcibly supplied to the cathode 40 by operating thefan, thereby supplying oxygen to the cathode 40.

In the present invention, the supply of oxygen through such a forciblemethod may be expressed as an air flow rate, which will be describedbelow.

In addition, the application example 100 of the oxygen generatoraccording to the present invention may further include a watercollection line 90 for collecting water (H₂O) generated at the cathode40 in the water supply source 70.

Subsequently, referring to FIGS. 2 to 4, the application example 100 ofthe oxygen generator device according to the present invention includesa first outer frame portion 110 positioned outside the anode 30 and asecond outer frame portion 120 positioned outside the cathode 40.

In this case, the first outer frame portion 110 includes a first outerframe 111, a water inlet 112 positioned at one side of the first outerframe 111, and an oxygen outlet 113 positioned at the other side of thefirst outer frame 111.

That is, water (H₂O) supplied from the water supply source 70 may besupplied to the anode 30 through the water inlet 112, hydrogen ions(H⁺), oxygen (O₂), and electrons may be generated by electrolyzing water(H₂O) at the anode, and the generated oxygen (O₂) may be dischargedthrough the oxygen outlet 113.

In addition, the second outer frame portion 120 includes a second outerframe 121, an oxygen inlet 122 positioned at one side of the secondouter frame 121, and a water outlet 123 positioned at the other side ofthe second outer frame 121.

That is, oxygen may be supplied to the cathode 40 through the oxygeninlet 122, oxygen (O₂) in air supplied from the air supply unit (notshown) reacts with hydrogen ions (H⁺) being moved by passing through theelectrolyte membrane 50 to generate water (H₂O) at the cathode, and thegenerated water (H₂O) may be discharged through the water outlet 123.

In this case, as described above, water (H₂O) generated at the cathode40 may be collected in the water supply source 70 through the watercollection line 90 or may be discharged through any discharge line.

Subsequently, referring to FIGS. 2 to 4, the application example 100 ofthe oxygen generator according to the present invention includes agasket 130 positioned between the first outer frame portion 110 and thesecond outer frame portion 120.

The gasket 130 includes a gasket frame 131 coupled to the first outerframe portion 110 and the second outer frame portion 120 and a hollowportion 132 formed inside the gasket frame 131.

The gasket frame 131 may be made of Teflon or silicon.

In this case, as shown in FIG. 3, the membrane-electrode assembly 60including the anode 30, the cathode 40, and the electrolyte membrane 50provided between the anode and the cathode may be positioned in thehollow portion 132.

The gasket 130 may support the membrane-electrode assembly 60 and mayalso prevent water supplied to the membrane-electrode assembly 60 orwater generated in the membrane-electrode assembly 60 from flowing tothe outside.

Hereinafter, the oxygen generator according to the present inventionwill be described in more detail.

First, the anode 30 may include a first support, a first catalyst layerpositioned at one side of the first support, and a first gas diffusionlayer positioned at the other side of the first support.

The first support may include carbon black, Ketjen black, acetyleneblack, an activated carbon powder, a carbon molecular sieve, carbonnanotubes, activated carbon having fine pores, mesoporous carbon, aconductive polymer, or a mixture thereof.

The first catalyst layer may include at least one catalyst for an OERselected from the group consisting of metals including platinum (Pt),iridium (Ir), ruthenium (Ru), nickel (Ni), manganese (Mn), cobalt (Co),iron (Fe), titanium (Ti), rhenium (Re), niobium (Nb), vanadium (V),sulfur (S), and molybdenum (Mo) and the metals combined with an oxide, anitride, a carbide, a phosphide, and a sulfide. The first catalyst layermay be in a state of being supported on the first support.

Next, the cathode 40 may include a second support, a second catalystlayer positioned at one side of the second support, and a second gasdiffusion layer positioned at the other side of the second support.

The second support may include at least one material selected from thegroup consisting of carbon or transition metals combined with an oxide,a nitride, a carbide, a phosphide, and a sulfide.

The second catalyst layer may include at least one catalyst for an ORRselected from the group consisting of Pt, palladium (Pd), Ir, gold (Au),silver (Ag), and an alloy thereof. The second catalyst layer may be in astate of being supported on the second support.

In this case, the alloy of Pt, Pd, Ir, Au, and Ag may be an alloy of ametal selected from the group consisting of Pt, Pd, Ir, Au, and Ag witha transition metal, an alkali metal, or a lanthanide group metal.

The transition metal may be at least one selected from the groupconsisting of scandium (Sc), Ti, V, chromium (Cr), Mn, Fe, Co, Ni,copper (Cu), zinc (Zn), zirconium (Zr), Nb, Mo, technetium (Tc), Ru,rhodium (Rh), hafnium (Hf), tantalum (Ta), tungsten (W), Re, and osmium(Os). The alkali metal may be at least one selected from the groupconsisting of potassium (K), rubidium (Rb), cesium (Cs), beryllium (Be),magnesium (Mg), calcium (Ca), chromium (Cr), barium (Ba), and radium(Ra). The lanthanide group metal may be at least one selected from thegroup consisting of lanthanum (La), yttrium (Y), cerium (Ce),praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm),europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), ytterbium(Yb), and lutetium (Lu).

In addition, alternatively, the second catalyst layer may include acatalyst for an ORR having an Fe—N coordination bond, and the secondcatalyst layer may be in a state of being supported on the secondsupport.

In this case, in the present invention, the second catalyst layer, whichincludes a catalyst for a cathode, may use an Fe—N—C catalyst, and theFe—N—C catalyst may inhibit an HER and promote an ORR, that is, an HERmay not occur. Thus, the Fe—N—C catalyst may be used throughout a widerange of potentials.

On the other hand, the first gas diffusion layer and the second gasdiffusion layer function to allow a reaction gas to easily access thecatalyst layer. In particular, the first gas diffusion layer of theanode should function to allow water supplied from the water supply unitto pass therethrough, and the second gas diffusion layer of the cathodeshould function to allow oxygen supplied from the air supply unit topass therethrough.

As long as a gas diffusion layer may perform such a function, the gasdiffusion layer is not particularly limited, and for example, the gasdiffusion layer may include carbon paper, carbon cloth, or a metal sheethaving in a mesh form.

The metal sheet in the mesh form may be a stainless steel-based mesh, atitanium-based mesh, or a nickel-based mesh.

However, the materials of the first gas diffusion layer and the secondgas diffusion layer are not limited in the present invention.

Next, the electrolyte membrane 50 may function as a transfer passagethrough which hydrogen ions generated at the anode are transferred tothe cathode and may be a polymer electrolyte membrane having hydrogenion exchange characteristics or a polymer electrolyte membrane havinghydroxide ion exchange characteristics.

For example, the electrolyte membrane 50 may include at least oneselected from the group consisting of a perfluoro-based protonconductive polymer membrane, a sulfonated polysulfone copolymer, asulfonated poly(ether-ketone)-based polymer, a perfluorinated sulfonicacid group-containing polymer, a sulfonated polyether ether ketone-basedpolymer, a polyimide-based polymer, a polystyrene-based polymer, apolysulfone-based polymer, and a clay-sulfonated polysulfonenanocomposite.

In addition, the electrolyte membrane may include an aqueous solvent,and the aqueous solvent may be at least one selected from H₂SO₄, HClO₄,K₂SO₄, Na₂SO₄, H₃PO₄, H₄P₂O₇, K₂PO₄, Na₃PO₄, K₃PO₄, HNO₃, KNO₃, andNaNO₃.

A thickness of the electrolyte membrane may be, for example, in a rangeof 5 μm to 300 μm, 10 μm to 200 μm, or 15 μm to 100 μm. In this case,when the thickness of the electrolyte membrane is less than 5 μm,mechanical strength may be lowered and chemical stability may belowered, and when the thickness of the electrolyte membrane exceeds 300μm, electrical resistance may be increased.

On the other hand, in order to constitute the membrane-electrodeassembly, the bonding of the anode, the cathode, and the electrolytemembrane is required, and such bonding may be performed through athermal pressing method or the like. For example, by using a hot pressdevice, a thermal press bonding process may be performed at atemperature ranging from of 120° C. to 150° C. and a pressure rangingfrom 50 kgf/cm² to 200 kgf/cm² for 0.1 minutes to 10 minutes.

MODES OF THE INVENTION

Hereinafter, Experimental Examples according to the present inventionwill be described, but the scope of the present invention is not limitedto the following Experimental Examples.

Experimental Example 1

On a nafion electrolyte membrane, Pt/C as a catalyst was applied on acathode, and an iridium oxide catalyst having a nanoporous structure wasapplied on an anode using a spray method, a decal method, or the like.

Water was supplied to the anode through a water supply source, andoxygen was generated from water through an OER. In this case, generatedhydrogen ions moved through the nation electrolyte membrane, and an ORR,through which oxygen in air is reduced to generate water, occurred atthe cathode.

FIG. 5 is a graph showing a change in oxygen generation current densityaccording to a voltage of Experimental Example 1.

In FIG. 5, Pt/C—IrO₂ (Air-Water) means that Pt/C was used as a cathodecatalyst, IrO₂ was used as an anode catalyst, air was supplied to thecathode through a separate air supply unit, and water was supplied tothe anode through a separate water supply source. Hereinafter, theexpressions have the same meaning.

Referring to FIG. 5, when a voltage of 1.4 V was applied, a currentdensity of about 1,000 mA/cm² was obtained, and in this case, it wasconfirmed that an amount of oxygen generated at the anode was about 350cm³/min (STP).

Experimental Example 2

On a nafion electrolyte membrane, platinum as a catalyst was applied ona cathode, and an iridium oxide catalyst having a nanoporous structurewas applied on an anode using a spray method, a decal method, or thelike.

In this case, unit cell evaluation was performed in the same manner asin Experiment Example 1 described above except that the supply of waterto the anode through a water supply source was cut off and the supply ofair to the cathode through an air supply unit was cut off.

FIG. 6 is a graph showing a change in oxygen generation current densityaccording to a voltage of Experimental Example 2.

In FIG. 6, Pt/C—IrO₂ (Non Air-Water) means that Pt/C was used as acathode catalyst, IrO₂ was used as an anode catalyst, the supply ofwater to the anode through the water supply source was cut off, and thesupply of air to the cathode through the air supply unit was cut off.

Referring to FIG. 6, when a voltage of 1.4 V was applied, a currentdensity of 0 mA/cm² was obtained, and in this case, when air was notsupplied to the cathode and water was not supplied to the anode, it wasconfirmed that an OER, through which oxygen is generated, did not occurat the anode.

Experimental Example 3

On a nation electrolyte membrane, platinum as a catalyst was applied ona cathode, and an iridium oxide catalyst having a nanoporous structurewas applied on an anode using a spray method, a decal method, or thelike.

In this case, unit cell evaluation was performed in the same manner asin Experiment Example 1 described above except that the supply of air tothe cathode through an air supply unit was cut off.

FIG. 7 is a graph showing a change in oxygen generation current densityaccording to a voltage of Experimental Example 3.

In FIG. 7, Pt/C—IrO₂ (Non Air-Water) means that Pt/C was used as acathode catalyst, IrO₂ was used as an anode catalyst, water was suppliedto the anode through a water supply source, and the supply of air to thecathode through the air supply unit was cut off.

Referring to FIG. 7, when a voltage of 1.4 V was applied, a currentdensity of 0 mA/cm² was obtained, and in this case, when air was notsupplied to the cathode, an ORR did not occur, and thus, it wasconfirmed that an OER did not occur at the anode.

Experimental Example 4

On a nafion electrolyte membrane, platinum as a catalyst was applied ona cathode, and an iridium oxide catalyst having a nanoporous structurewas applied on an anode using a spray method, a decal method, or thelike.

Water was supplied to the anode through a water supply source, but thesupply of air to the cathode was cut off and a voltage was applied up to1.8 V to perform unit cell evaluation.

FIG. 8 is a graph showing a change in oxygen generation current densityaccording to a voltage of Experimental Example 4.

Referring to FIG. 8, when air was not supplied to the cathode, it wasconfirmed that constant current density was obtained only when a voltageof 1.4 V or higher was applied, but in this case, it was confirmed thatan HER occurred at the cathode.

That is, Experimental Example 4 showed a contrasting result with Example1 in that when air was supplied to the cathode through the separate airsupply unit and water was supplied to the anode through the separatewater supply source, current density was obtained even when a voltage of0.6 V or more was applied. In addition, it was confirmed that an OERoccurred at the anode in Experimental Example 1 and an HER occurred atthe cathode in Experimental Example 4.

Experimental Example 5

On a nation electrolyte membrane, platinum as a catalyst was applied ona cathode, and an iridium oxide catalyst having a nanoporous structurewas applied on an anode using a spray method, a decal method, or thelike.

Water was supplied to the anode through a water supply source, air wassupplied to the cathode through an air supply unit, and an air flow ratewas changed from 5 ccm to 100 ccm to perform unit cell evaluation.

FIG. 9 is a graph showing a change in oxygen generation current densityaccording to a flow rate of air of Experimental Example 5.

Referring to FIG. 9, it was confirmed that as the air flow rate wasincreased, oxygen generation current density was increased, and it wasconfirmed that when 100 ccm of air was supplied and a voltage of 1.4 Vwas applied, a current of 1,000 A/cm² was obtained.

However, when an air flow rate was 5 ccm and 10 ccm, generated currentdensity was insufficient. Therefore, in the present invention, a supplyflow rate of air through the air supply unit may be 20 ccm or more.

Experimental Example 6

Unit cell evaluation was performed in the same manner as in ExperimentalExample 1 except that on a nafion electrolyte membrane, an iridium oxidecatalyst having a nanoporous structure was used at an anode and anothercatalyst, i.e., a catalyst of Fe/N/C was used at a cathode instead of acatalyst of Pt/C.

Here, when Fe/N/C was used as a catalyst of the cathode, unit cellevaluation was performed by being divided into a case (1) in which waterwas supplied to the anode through a water supply source and air wassupplied to the cathode through an air supply unit (Air-Water), a case(2) in which water was supplied to the anode through the water supplysource but the air supply unit was blocked and thus air was not suppliedto the cathode (Non Air-Water), and a case (3) in which the water supplysource was blocked and thus water was not supplied to the anode and theair supply unit was blocked and thus air was not supplied to the cathode(Non Air-Non Water).

FIG. 10 is a graph showing a change in oxygen generation current densityaccording to a voltage of Experimental Example 6.

Referring to FIG. 10, when a voltage of 1.4 V was applied, a currentdensity of about 300 mA/cm² was obtained, and in this case, it wasconfirmed that an amount of oxygen generated at the anode was about 140cm³/min (STP).

However, even in the case of Experimental Example 6, in the case (2) inwhich water was supplied to the anode through the water supply sourcebut the air supply unit was blocked and thus air was not supplied to thecathode (Non Air-Water) and the case (3) in which the water supplysource was blocked and thus water was not supplied to the anode and theair supply unit was blocked and thus air was not supplied to the cathode(Non Air-Non Water), when a voltage of 1.4 V was applied, a currentdensity of 0 mA/cm² was obtained, and in this case, when air was notsupplied to the cathode, an ORR did not occur, and thus, it wasconfirmed that an OER did not occur at the anode.

Experimental Example 7

Unit cell evaluation was performed in the same manner as in ExperimentalExample 1 except that platinum as a catalyst was used at a cathode andthe same platinum catalyst as the cathode was used at an anode.

Here, when PT/C was used as a catalyst of the cathode and the anode,unit cell evaluation was performed by being divided into a case (1) inwhich water was supplied to the anode through a water supply source andair was supplied to the cathode through an air supply unit (Air-Water)and a case (2) in which water was supplied to the anode through thewater supply source but the air supply unit was blocked and thus air wasnot supplied to the cathode (Non Air-Water).

FIG. 11 is a graph showing a change in oxygen generation current densityaccording to a voltage of Experimental Example 7.

Referring to FIG. 10, in a case in which a catalyst of Pt/C was used,when a voltage of 1.4 V was applied, a current density of about 500mA/cm² was obtained. Thus, it was confirmed that an OER occurred evenwhen an anode catalyst varied.

However, even in the case of Experimental Example 7, in the case (2) inwhich water was supplied to the anode through the water supply sourcebut the air supply unit was blocked and thus air was not supplied to thecathode (Non Air-Water), when a voltage of 1.4 V was applied, a currentdensity of 0 mA/cm² was obtained, and in this case, when air was notsupplied to the cathode, an ORR did not occur, and thus, it wasconfirmed that an OER did not occur at the anode.

Experimental Example 8

Unit cell evaluation was performed in the same manner as in ExperimentalExample 1 except that platinum as a catalyst was used at a cathode and aruthenium oxide catalyst was used at an anode.

In this case, water was supplied to the anode through a water supplysource, and air was supplied to the cathode through an air supply unitto perform unit cell evaluation.

FIG. 12 is a graph showing a change in oxygen generation current densityaccording to a voltage of Experimental Example 8.

Referring to FIG. 12, in a case in which the ruthenium oxide catalystwas used at the anode, when a voltage of 1.4 V was applied, a currentdensity of about 1,200 mA/cm², which was increased as compared with acase in which an iridium oxide catalyst was used at an anode, wasobtained, and in this case, it was confirmed that an amount of oxygengenerated at the anode was about 420 cm³/min (STP).

Therefore, it can be seen that an amount of oxygen generated at theanode may be increased by varying a catalyst of the anode.

As described above, in the present invention, it is possible toconstitute an oxygen generator for generating oxygen (O₂) using a simpleconfiguration including a membrane-electrode assembly 60, a power supply20 capable of applying a certain amount of power, a water supply source70 capable of supplying water to an anode of the membrane-electrodeassembly, and an air supply unit 80 for supplying oxygen to a cathode ofthe membrane-electrode assembly.

Therefore, in the present invention, an electrochemical oxygen generatorcan be provided such that oxygen is generated without noise andvibration using an electrochemical method and the electrochemical oxygengenerator is miniaturized due to a simple device configuration.

Although the embodiments of the present invention has been describedwith reference to the accompanying drawings, it should be understoodthat those skilled in the art can carry out other modifications withoutchanging the technical spirit or essential features of the presentinvention. Therefore, it should be understood that the embodimentsdescribed herein are illustrative and not restrictive in all aspects.

What is claimed is:
 1. An oxygen generator, wherein an oxygen reductionreaction occurs at a cathode to which outside air is introduced, anoxygen evolution reaction occurs at an anode to which water is supplied,and an air flow rate at which the outside air flows is 20 ccm or more.2. The oxygen generator of claim 1, wherein oxygen (O₂) is generated atthe anode using the oxygen evolution reaction (OER), and water (H₂O) isgenerated at the cathode using the oxygen reduction reaction (ORR). 3.An oxygen generator comprising: a membrane-electrode assembly includingan anode connected to a first electrode of a power supply, a cathodeconnected to a second electrode of the power supply, and an electrolytemembrane provided between the anode and the cathode; a water supplysource configured to supply water to the anode; and an air supply unitconfigured to supply oxygen to the cathode, wherein oxygen (O₂) isgenerated at the anode using an oxygen evolution reaction (OER), andwater (H₂O) is generated at the cathode using an oxygen reductionreaction (ORR).
 4. The oxygen generator of claim 3, further comprising:a water collection line configured to collect water (H₂O) generated atthe cathode in the water supply source.
 5. The oxygen generator of claim4, further comprising: a first outer frame portion positioned outsidethe anode and a second outer frame portion positioned outside thecathode, wherein the first outer frame portion includes: a first outerframe; a water inlet positioned at one side of the first outer frame;and an oxygen outlet positioned at the other side of the first outerframe, wherein the second outer frame portion includes: a second outerframe; an oxygen inlet positioned at one side of the second outer frame;and a water outlet positioned at the other side of the second outerframe.
 6. The oxygen generator of claim 5, wherein water (H₂O) suppliedfrom the water supply source is supplied to the anode through the waterinlet, wherein, at the anode, hydrogen ions (H⁺), oxygen (O₂), andelectrons are generated by electrolyzing water (H₂O) and the generatedoxygen (O₂) is discharged through the oxygen outlet, and wherein, at thecathode, oxygen (O₂) in air supplied from the oxygen inlet reacts withhydrogen ions (H⁺) being moved by passing through the electrolytemembrane to generate water (H₂O) and the generated water (H₂O) isdischarged through the water outlet.
 7. The oxygen generator of claim 3,wherein the anode includes a first support and a first catalyst layerpositioned at one side of the first support, wherein the first supportincludes carbon black, Ketjen black, acetylene black, an activatedcarbon powder, a carbon molecular sieve, carbon nanotubes, activatedcarbon having fine pores, mesoporous carbon, a conductive polymer, or amixture thereof, and wherein the first catalyst layer includes an oxygenevolution reaction (OER), wherein the oxygen evolution reaction (OER) isselected from the group consisting of platinum (Pt), iridium (Ir),ruthenium (Ru), nickel (Ni), manganese (Mn), cobalt (Co), iron (Fe),titanium (Ti), rhenium (Re), niobium (Nb), vanadium (V), sulfur (S),molybdenum (Mo), an oxide thereof, a nitride thereof, a carbide thereof,a phosphide thereof, a sulfide thereof, and a combination thereof. 8.The oxygen generator of claim 3, wherein the cathode includes a secondsupport and a second catalyst layer positioned at one side of the secondsupport, wherein the second support includes a material selected fromthe group consisting of carbon, a transition metal oxide, a transitionmetal nitride, a transition metal carbide, a transition metal phosphide,a transition metal sulfide, and a combination thereof, and wherein thesecond catalyst layer includes a catalyst for ORR, wherein the catalystfor ORR is selected from the group consisting of platinum (Pt),palladium (Pd), iridium (Ir), gold (Au), silver (Ag), an alloy thereof,and a combination thereof.
 9. The oxygen generator of claim 3, whereinthe cathode includes a second support and a second catalyst layerpositioned at one side of the second support, wherein the second supportincludes a material selected from the group consisting of carbon, atransition metal oxide, a transition metal nitride, a transition metalcarbide, a transition metal phosphide, and a transition metal sulfide,and a combination thereof, and wherein the second catalyst layerincludes a Fe—N—C catalyst.
 10. The oxygen generator of claim 9, whereinthe Fe—N—C catalyst inhibits hydrogen evolution reaction and promotesORR.